In recent years, active studies have been conducted on SON (Self Organizing Network), which autonomously optimizes radio parameters and network configurations in wireless communication systems such as cellular systems, in view of operating expense (OPEX) reduction and the like. Standardization of SON functions is under way also in LTE (Long Term Evolution) of 3GPP (3rd Generation Partnership Project) (NPL 1).
SON includes functions such as:    Self-Configuration;    Self-Optimization;    Self-Healing.
These are technologies for accomplishing respective different objectives. Of them, Self-Optimization includes categories such as: optimization of cell coverage and capacity (Coverage and Capacity Optimization: CCO); optimization of handover parameters (Mobility Robustness Optimization: MRO); and optimization of load balancing (Mobility Load Balancing: MLB) (NPL 2).
In SON, a problem is recognized by using radio quality information reported from terminals and communication quality statistical information compiled by a base station, and a radio parameter of the base station is autonomously optimized so that the problem will be mended. For the information reported from terminals, those prescribed in 3GPP are used, but many of current studies on SON employ radio quality measured by terminals in wirelessly connected state (RRC Connected state).
On the other hand, 3GPP Release 10 newly prescribes MDT (Minimization of Drive Test) with the view of suppressing (minimizing) drive tests related to radio network operations management to the least extent possible. MDT prescribes an immediate reporting mode (Immediate MDT), in which a terminal in wirelessly connected state performs measurement and reporting, and a recording and reporting mode (Logged MDT), in which a terminal in idle state (RRC Idle state) records a measurement result and reports it when falling in wirelessly connected state. Moreover, information to be measured includes not only radio quality information but also a measuring terminal's location information (for example, information of GNSS (Global Navigation Satellite System) such as GPS (Global Positioning System)).
Accordingly, in SON, it is possible to optimize base station's parameters, based on radio quality information measured by terminals in immediate reporting mode or recording and reporting mode.